The condensation of sugars to soluble oligosaccharides is of great economic, nutritional, and therapeutic relevance. It is well known that the consumption of excess sugar by humans and animals has been linked to a variety of negative health indications, such as obesity and diabetes. It is further established that diets rich in fiber, such as indigestible oligosaccharides and polysaccharides, promote health and well being. Some dietary fibers interact favorably with the ecosystem of human and animal gut micro biota, stimulating the growth of advantageous gut bacteria, inhibiting the growth of undesirable gut bacteria, and inhibiting the ability of pathogenic bacteria to colonize the gut.
Oligosaccharides can be added to foods to empart favorable flavor, mouth feel, and consistency. Furthermore, oligosaccharides that are not digestible by humans contribute little or no caloric value to foods. There is significant commercial interest in replacing some portion of the raw sugar ingredients in foods with oligosaccharides to reduce the caloric content of those foods and improve their impact on the human microbiome. There is interest in incorporating oligosaccharide ingredients to reduce the sugar content and enhance the dietary fiber content of breakfast cereals, granola and other type of bars, yogurt, ice cream, breads, cake mixes, and nutritional shakes and supplements.
There is additional interest in incorporating oligosaccharide ingredients into animal feed to improve its nutritional quality. Oligosaccharides can be added to animal feed to improve gut health, increase weight gain, and promote feed efficiency. Furthermore, oligosaccharides that are not digestible by animals pass through the stomach and upper digestive system and can be fermented by gut micro-organisms. There is commercial interest in incorporating oligosaccharides into poultry, swine, aquaculture, and ruminant diets to improve the animal microbiome.
To achieve objectives pertaining to improved human and animal nutrition and health, oligosaccharides with a particular structure or range of structural properties are desired. At present, however, such oligosaccharides are limited to those obtained from sources such as corn meal, yeast bodies, dairy products, inulin, gums (such as guar gum or acacia gum), pectins, hemicellulose extracts, and other such agricultural and industrial food products. In other cases, oligosaccharides are produced by fermentation, roasting of starches and grains, and by polymerizing glucose in the presence of aqueous acids. The types of oligosaccharides obtained by biological production are limited in the variety of chemical structures that can be produced, the high cost of industrial fermentations, and the complex purification processes required to remove salts, buffers, and other fermentation byproducts to render the oligosaccharides suitable for human consumption.
Methods known in the art are limited in the variety of oligosaccharide structures that can be produced, and often have additional costly production steps. These can include neutralizing and/or removing aqueous acids or their salts, de-colorizing the product to a suitable level, and isolation and disposal of used catalyst that cannot be recycled.
As such, there is an ongoing need for improved methods of producing oligosaccharides on a commercially-viable scale.